<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <!-- 两个相同字符串之间的最长子字符串 -->
    <script>
      var maxLengthBetweenEqualCharacters = function (s) {
        let max = 0
        for (let i = 0; i < s.length; i++) {
          let last = s.lastIndexOf(s[i])
          if (last) {
            max = Math.max(max, last - i)
          }
        }
        return max - 1
      }
      console.log(maxLengthBetweenEqualCharacters('aa'))
    </script>
  </body>
</html>
